Crankcase vent tube extension & routing

[flybikedave]

I'm working on adding a crankcase vent tube extension, with "duckbilled" tip as shown in previous thread photos. I understand the best results come from turning the tube outlet to a 10:30 o'clock position and routing the tube over the top of the crankcase near the cylinder base, towards the firwall and down towards the belly. Questions: the old aluminum tube is badly deformed and the whistle hole is taped up by previous owner. Can I just use a rubber hose for the entire route, or do I need aluminum tube over the engine? How about copper tubing? And what is the function of the whistle hole and is it really necessary? It it is necessary, how do I orient the hole on my new tube? Any help/comments are greatly appreciated.
PS: Am enjoying my new matching left hand door and window here in south LA, where it is in the upper 70's today where 2 open doors are still possible.

 

[fasken]

 

[Sbaber]

 

[bob turner]

 

[AOP]

 

[luvcubs]

 

[flybikedave]

 

[cubdriver2]

 

[flybikedave]

 

[bob turner]